Abstract:

We examined changes in muscle power output and fibercharacteristics following a 3 d·wk21, 8-week plyometric andaerobic exercise program. Male subjects (n519) were ran-domly assigned to either group 1 (plyometric training) orgroup 2 (plyometric training and aerobic exercise). The ply-ometric training consisted of vertical jumping, bounding,and depth jumping. Aerobic exercise (at 70% maximum heartrate) was performed for 20 minutes immediately followingthe plyometric workouts. Musclebiopsy specimens were col-lected from the musculus vastus lateralis before and aftertraining. Type I and type II fibers wereidentified and cross-sectional areas calculated. Peak muscle power output, mea-sured using a countermovement vertical jump,significantlyincreased from pretraining to posttraining for group 1 (2.8%)and group 2 (2.5%). Each groupdemonstrated a significantincrease in fiber area from pretraining to posttraining fortype I (group 1, 4.4%; group 2, 6.1%) and type II (group 1,7.8%; group 2, 6.8%) fibers, but there were no differencesbetween the groups. Following plyometric training, there isan increased power output that may in part be related tomuscle fiber size.